Error 80048821 is another Windows Live Messenger error that looks something like this:
Sorry, we were unable to sign you in to the .NET Messenger Service at this time.
Please try again later.
In most of the cases, you are unable to sign into Windows Live Messenger because your password is not correct or your username is non-existing one. So this is the first thing you should check. Are your username and password correctly typed? Try to type them in slowly and see what happens. If these are correct and you are still getting the annoying error message, you can try to solve the problem by doing the following:
Set the time and date on your computer. Just click twice to make sure that these settings are OK. Go to http://passport.com and change your password. It is better for you to choose a shorter password that does not exceed ten characters. When you have done that, see if you can sign in with the new password. Firewall is also one of the possible problem-causing features, so if you have on running, turn it off. Sometimes the permission to access Messenger is denied by these features. You can turn off the firewall and see what happens, or you can first remove Messenger form the lost of allowed programs and then add it again.
Sometimes firewall can cause trouble, even if it is turned off. Restart the computer to make sure that firewall is disabled. You can even uninstall the firewall. Next thing you can try is to clear the cookies and Internet Explorer cache. Start the Internet Explorer, go to the Tools, choose Internet Options, then Delete Files and after that – Delete cookies. Go to Security settings. Start the Explorer and choose Tools; then click Internet options, Advanced, find Security and then un-check the Check for server certificate revocation option. Check the option “Use SSL 2.0” and “Use SSL 3.0”. Click OK and that should be it.
Go to the start menu, click Run and type in this: regsvr32 softpub.dll; OK, then type in regsvr32 wintrust.dll, click OK. Type: regsvr32 initpki.dll and click OK.
In case you are a MSN 7 user, go to the Tools, choose Options, click the Connection Category and then the Advanced settings. All of these should be unchecked. Double click OK and that should be it! If you do not succeed in solving the problem, get some professional assistance.